It is so nice to learn of your interest in physics and astronomy as well as to learn that you aspire to be an aerospace engineer. I am a Mechanical Engineer myself and while some courses I took in school were tough and needed a lot of effort, they were certainly doable. Going to med school is no easy task when compared to engineering. I would say they are both strenuous.
Being a good doctor or a good engineer and acing in your respective field will take both effort and perseverance from your end. Just as you are getting advice from an engineer,I would encourage you to reach out to a doctor as well and hear from them first hand about their educational experience. When you have enough data about both professions, you will be able to make a choice based on both your interest and capability level. There are a lot of jobs available for engineers all around the world. It completely depends on what you want to do and over the 4 years of engineering, you might discover new passions and interests which can lead to many innovative careers.
If you need additional advice, please feel free to reach out to me via email.